Today at division 2 contest, I have submitted the A no. problem at 14th min and it passed the pretest I then turned to problem B.But after sometimes at 33th min I saw that another solution for problem A have been submitted from my ID.But I didn't submit that one. And the code was also different from my code. Is that any mismanagement problem by Codeforces or my ID has been hacked??
It's really probable, that your account has been hacked.
I can advise you to change your password (maybe even your email account's password too).
Thanks,for your kind suggestion...